The present invention relates generally to integrated circuits (ICs). More particularly, the invention relates to the repairing of ICs with defective conductive lines.
An integrated circuit (IC) comprises a multiplicity of circuit blocks, each containing various circuit components. Conductive lines are provided, interconnecting the circuit components and circuit blocks to perform the desired functions. The conductive lines typically comprise metal and are generally relatively long. As such conductive lines are prone to defects (e.g., open connection) during the manufacturing process. A defective conductive line renders the circuit components or blocks coupled thereto non-accessible, resulting in a non-usable IC.
To address the problem associated with defective conductive lines, additional circuit components (e.g., redundant or spare circuitry) can be provided. FIG. 1 shows a portion 100 of an IC with conventional redundant circuitry. The IC portion includes a plurality of identical circuit blocks 1011-x. A circuit block comprises a circuit element 110 coupled to, for example, a logic block 120 via a conductive line 130. A spare or redundant circuit block 115, which is essentially identical to circuit blocks 110, is provided. If the conductive line 1304 is defective (e.g., open connection 132), then circuit block 1014 is replaced with the redundant circuit block using, for example, conventional fuse techniques.
However, such conventional redundancy techniques are ineffective to repair defective bank column select lines (BCLSs) of a hierarchical column select architecture. Referring to FIG. 2, a memory bank 200 of a memory IC is shown. The bank includes a hierarchical column select switch 260 coupled to a plurality of columns 201, each comprising a bitline pair coupled to a sense amplifier (SA). Illustratively, the bank comprises 128 columns. Bank column select lines (BCSLs) and global column select lines (GCSLs) are coupled to the column select switch. The bank column select signals on BCSLs select a group of columns (e.g., 64). The global column select signals on the GCSLs select one column from the selected group of columns for sensing by the secondary sense amplifier 280 coupled to the switch by a master data line (MDQ) 275. If a defect 232 occurs in BCSL 2900, a conventional redundant circuit block comprising 64 columns of memory cells, BCSL, and the bank column decoder 281 would be required to repair the defective BCSL. Such a redundant circuit block would require significant chip area, which undesirable increases manufacturing cost
As evidenced from the above discussion, it is desirable to provide a technique to effectively repair defective BCSLs.
The invention relates to improved redundancy in ICs. In one embodiment, the redundancy includes providing multiple conductive paths in a circuit portion between a circuit element and a logic block. Providing multiple conductive paths enables the circuit portion to function properly without the need for fusing to repair a defect in the conductive path. Such a redundancy scheme, in one embodiment, is implemented in a memory system with a hierarchical column select architecture, particular in the BCSL lines.